1. Field of the Invention
The present invention relates to a micro actuator and an ink jet printer head fabricated using the same, and more particularly, the present invention relates to a micro actuator which is manufactured by patterning a piezoelectric element employing an etching technique and to an ink jet printer head which is fabricated using the micro actuator.
2. Description of the Related Art
Generally, a micro actuator includes a lower structure which has a vibrating plate and a chamber, a piezoelectric element which is coupled onto a substrate and is mechanically deformed when electric power is applied thereto, and an electrodes) which transfers electric power to the piezoelectric element.
Referring to FIG. 1, there is shown a cross-sectional view illustrating an example of a micro actuator according to the related art. In the micro actuator as shown in FIG. 1, electric power is supplied to electrode 118 and electrode 114, which is formed on a diaphragm 111 formed over substrate 110, and electrode 118, a piezoelectric element 116 vibrates while repeating deformation and return.
In order to manufacture a micro actuator, methods as described below have been used.
In a first method, a lower electrode is formed on a substrate which is patterned into a thin and precise size and then, is baked at a temperature of no less than 1200xc2x0 C. Then, piezoelectric element paste is formed on the lower electrode by a screen printing method and baked at a high temperature of no less than 1000xc2x0 C. Thereafter, an upper electrode is formed on the piezoelectric element and baked at a temperature of about 800xc2x0 C., whereby the micro actuator is manufactured.
In the case that a thin film or a thick film of a piezoelectric element is directly formed on a substrate, the substrate is likely to be deformed due to a high sintering temperature of the piezoelectric element. Accordingly, ceramic which is capable of enduring the sintering temperature of the piezoelectric element, is used as the substrate, and zirconia is widely used among various ceramic materials.
Also, when the screen printing method is used, a problem is caused in that it is difficult to precisely pattern the piezoelectric element paste to a desired fine pattern.
In a second method for manufacturing a micro actuator, a piezoelectric element which is separately formed or manufactured is bonded to a metal substrate by a third material and then, the prepared piezoelectric element plate is machined to have a predetermined size thereby to construct actuators of a desired number. Alternatively, in the second method, a piezoelectric element which is machined to a size which is suitable for one actuator, is bonded onto a metal substrate to construct an actuator.
In this method, since metal is used as the substrate, an advantage is provided in that a process of high precision such as fine machining of ceramic can be avoided.
However, in the case of machining the piezoelectric element plate in order to obtain a desired number of actuators, integration density cannot but be decreased due to a limit in machining, whereby precision and reliability of end products are reduced and it is difficult to achieve competitiveness in quality and productivity.
In addition, in the case that the piezoelectric element which is machined to a predetermined size is bonded onto the metal substrate, since yield rate is reduced for respective actuators, it is difficult to simultaneously manufacture a plurality of actuators.
In order to solve the problems encountered in the related art, in Korean Patent Application No. 98-29816 which was filed by the applicant of the present application, there is disclosed a method for manufacturing a micro actuator, in which a piezoelectric element having a predetermined thickness is attached onto a substrate and then is etched, thereby to form a plurality of piezoelectric elements having a desired thickness.
In this method, when manufacturing the micro actuator, a remaining portion of the piezoelectric element, except for a portion which is integrated with the substrate and used in driving a cell, is wholly removed by etching.
When manufacturing the micro actuator using the above method, advantages are provided in that the problems encountered in the related art can be resolved.
However, the method for manufacturing the micro actuator suffers from defects in that since an amount of the piezoelectric element which is removed by the etching process is fairly large, etching solution is wasted and rapidly degraded. Moreover, the etching solution can impose harmful influences on the substrate.
While the aforementioned micro actuator can be used to manufacture various articles, an ink jet printer head can be exemplified as a typical example which can be manufactured using the micro actuator.
FIG. 2 is a cross-sectional view illustrating an example of an ink jet printer head according to the related art.
As can be readily seen from FIG. 2, an ink jet printer head includes a nozzle plate 222 which is formed with a nozzle 220, a reservoir plate 226 which is formed with a reservoir 224, a fluid passage plate 230 which is formed with a fluid passage 228, a restrictor plate 234 which is formed with a restrictor 232, a chamber plate 210 which defines a chamber 212, an actuator comprising an upper electrode 218, a piezoelectric element 216 and a lower electrode 214, which is formed on a substrate 211. The nozzle plate 222, the reservoir plate 226, the fluid passage plate 230, the restrictor plate 234, the chamber plate 210 and the actuator are sequentially stacked one upon another from bottom to top.
By the construction described above, ink moving paths such as the nozzle 220, the reservoir 234, the fluid passage 228, the restrictor 232 and the chamber 212, which have different sizes and configurations, are defined in the ink jet printer head.
Ink supplied from an ink container (not shown) is stored in the reservoir 224 and is supplied to the chamber 212 through the fluid passage 228. At this time, the restrictor 232 formed between the fluid passage 228 and the chamber 212 serves to keep velocity of ink flowing into the chamber 212 constant.
If voltage is applied to the upper electrode 218 and the lower electrode 214 of the micro actuator which is formed above the chamber 212, the piezoelectric element 216 is actuated, and by this actuation of the piezoelectric element 216, as volume of the chamber 212 is momentarily reduced, ink stored in the chamber 212 is injected through the nozzle.
Due to the fact that the ink jet printer head uses the micro actuator manufactured as described above in order to inject ink, the ink jet printer head also suffers from the same defects as described above with respect to the micro actuator.
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a micro actuator wherein a remaining portion of a piezoelectric element, except for a portion which is integrated with a substrate and used in driving a cell, is not wholly removed, and instead, only a boundary portion between a first piezoelectric element portion which is arranged above a space part and is actuated when voltage is applied thereto and a second piezoelectric element portion which is not arranged above the space part and is not actuated when voltage is applied thereto, is etched, thereby accomplishing economy and improving repeatability of processing.
Another object of the present invention is to provide an ink jet printer head which is manufactured using the micro actuator.
In order to achieve the above objects, according to one aspect of the present invention, there is provided a micro actuator comprising: a substrate having a space part which is integrally defined in the substrate and is opened only at a lower end thereof; a first piezoelectric element formed on the substrate in a first area which is arranged above the space part and actuated when voltage is applied thereto; a second piezoelectric element formed on the substrate in a second area which is not arranged above the space part and not actuated even when voltage is applied thereto; and an upper electrode formed on the first piezoelectric element; whereby rigidity of an entire structure is elevated and panel vibration is reduced, by the second piezoelectric element.
According to another aspect of the present invention, there is provided an ink jet printer head comprising: a substrate having a space part which is integrally defined in the substrate and is opened only at a lower end thereof; a nozzle plate formed under the substrate; a nozzle formed in the nozzle plate for injecting ink to record information; a chamber formed by the space part and the nozzle plate and containing ink; a first piezoelectric element formed on the substrate in a first area which is arranged above the space part and actuated when voltage is applied thereto; a second piezoelectric element formed on the substrate in a second area which is not arranged above the space part and not actuated even when voltage is applied thereto; and an upper electrode formed on the first piezoelectric element; whereby rigidity of an entire structure is elevated and panel vibration is reduced, by the second piezoelectric element.
According to still another aspect of the present invention, there is provided an ink jet printer head comprising: a substrate having a space part which is integrally defined in the substrate and is opened only at a lower end thereof; a restrictor plate formed under the substrate; a chamber formed by the space part of the substrate and the restrictor plate; a restrictor formed by the restrictor plate for keeping velocity of ink flowing into the chamber constant; a fluid passage plate formed under the restrictor plate; a fluid passage formed by the fluid passage plate for defining an ink flowing path; a reservoir plate formed under the fluid passage plate; a reservoir formed by the reservoir plate and storing ink; a nozzle plate formed under the reservoir plate; a nozzle formed in the nozzle plate for injecting ink to record information; a first piezoelectric element formed on the substrate in a first area which is arranged above the space part and actuated when voltage is applied thereto; a second piezoelectric element formed on the substrate in a second area which is not arranged above the space part and not actuated even when voltage is applied thereto; and an upper electrode formed on the first piezoelectric element; whereby rigidity of an entire structure is elevated and panel vibration is reduced, by the second piezoelectric element.